missig letter

[Pantagruel]

I am new to this forum so forgive me if I am posting this question in the wrong location. My computer is a ThinkPad T520. I cannot find a location on the forum for this particular model.

My issue: the button for the lower case letter 'n' does not work (I am writing this on another keyboard connected via USB)

I checked all the other letter buttons and they work OK. I did a keyboard driver check and it is up to date. I also uninstalled the keyboard via Control Panel but that did not solve the problem.

Can anyone help ?

[brchan]

If you take the keycap off and try pressing the exposed rubber dome, does the key register? The issue is almost certainly a faulty key and not driver related.

[Pantagruel]

Thank you.

The key does work without the plastic cap. I put the cap back on and the key works only if I press hard .

Any suggestion as to a cure? Would an electronic cleaner damage the keyboard ?

[rkawakami]

Inspect the underside of the keycap, the scissor mechanism it attaches to and the area surrounding, to see if there's any foreign material (dust/dirt, food, etc.) that's getting in the way. If nothing is there, then about the only "fix" would be to replace the entire keyboard.

Any kind of electronic contact cleaner would have to get under the rubber dome. That's where the actual switch is. You might be able to peel the rubber dome off, clean the traces/contact points with isopropyl alcohol but then you have the problem of re-attaching the dome. I'm not sure what kind of adhesive was used on it but if it's not sealed to the keyboard, then you risk getting the same problem with that key again (the dome could move and not make electrical contact or some junk could get under there and prevent the switch from working again).

Any specific T520 issues are handled in the topmost Classic ThinkPad Hardware forum of "ThinkPad T400/410/420 and T500/510/520 Series".

[Pantagruel]

I am learning to adapt to the situation. As long as pressing harder on the key continues to work, I will live with it.

Your input is much appreciated.

[Quardah]

Dear friend;

I do not know your level in electronics but i'll try to make it short. For a keyboard to work, 'contacts' has to be 'closed', which means once you press a key, a little sheet of metal comes in contact with 2 other little sheet of metal, which one of them is powered, and thus this power makes it's way to the endpoint, telling the computer that they key is pressed.

See this image for visual explaination, and focus on the little black bar under the key : http://static.tweakers.net/ext/f/Scgfzf ... X/full.gif

I guess you already knew this but i just want to be sure.

If you have to press the key really hard to make it work, it means the contact still exists, because in electronics, either there IS a contact or there IS NOT ('YES or NO' or 'TRUE or FALSE'). That being said, maybe there is something in between the contacts blocking the travel of the key part, or the parts of the contact sheets of metal are missing (broken with age).

If you wish to make it work and make sure it doesn't further degrade itself, i would recommend you disassemble the laptop keyboard and check it visually. If all of the keys are working fine except the 'n' key, inspect the 'n' key for any visual abnormalities and try to fix it using long needle noses. Or else you could simply change the keyboard module, which shouldn't be very expensive.

Hope this help!

[Pantagruel]

I am a senior who was raised on nuts and bolts. Electronics are a bit out of my reach (not to mention bits and bytes!) But with the help of kind people like you all, I usually manage to muddle through and fully enjoy the digital environment.

In fact, I find that having problems is a great way to learn new stuff. In this case I just learned that key board buttons are like electric switches. Interesting...

But I am curious : how does concurrently pressing the Shift key change the output (i.e. from lower case to upper case) ? If the two wires being connected remain the same, shouldn't the same circuit lead to the same result ?

[rkawakami]

All of the keyboard "switches" are actually connected to a keyboard controller or interface circuit. It monitors the status of each key and can tell if two (or more) keys are pressed at the same time. For your example, if the SHIFT key is held down while pressing a letter, it sends out a different code representing an upper case letter as opposed to lower case. The controller does the same when the CTRL and/or ALT keys are held down so that programs that rely on keyboard shortcuts (CTRL-C to copy, for example) can function properly.

For most of the Thinkpad keyboards I've seen, the actual switch contact is the rubber dome under the keycap. It is electrically conductive enough - when it's clean anyway - that the keyboard controller can tell when it's pressed. Here's an example:

http://forum.thinkpads.com/viewtopic.ph ... 13#p748813

[sktn77a]

You should be able to buy a used replacement keyboard on this forum's Marketplace listings for about $15.